Progression-Free Survival and Local Control After Stereotactic Body Radiotherapy (SBRT/SABR) for Treatment-Naive Oligometastatic Recurrent Prostate Cancer: A Multi-Institutional Individual Patient Data Analysis

Abstract

Evidence for metastasis-directed therapy in oligometastatic prostate cancer (PCa) recurrence is based on small and heterogeneous studies. This multi-institutional study pooled individual patient data from centers treating oligometastatic recurrent PCa with stereotactic body radiotherapy (SBRT), also termed stereotactic ablative radiotherapy (SABR). The analysis focused on treatment-naive patients to determine whether SBRT could delay disease progression. Eligible patients had three or fewer metastases. Distant progression-free survival (DPFS) and local progression-free survival (LPFS), reflecting local control, were estimated using the Kaplan-Meier method. Treatment-related toxicity was graded according to the Common Terminology Criteria for Adverse Events. Overall, 163 metastases were treated in 119 patients. Median DPFS was 21 mo (95% confidence interval, 15-26 mo). Lower radiotherapy dose predicted a higher local recurrence rate: 3-yr LPFS was 79% for patients treated with a biologically effective dose ≤100 Gy versus 99% for patients treated with >100 Gy (p=0.01). Seventeen patients (14%) had grade 1 toxicity and three patients (3%) had grade 2 toxicity. No grade ≥3 toxicity was observed. These findings provide a benchmark for future prospective trials of SBRT/SABR for oligometastatic prostate cancer recurrence. Patient summary: This multi-institutional analysis pooled available data on stereotactic body radiotherapy for limited prostate cancer metastases. We concluded that this metastasis-directed approach is safe and associated with prolonged progression-free survival.